Manufacturing processes such as those used for the production of electronic devices, flat panel displays, and lithography masks and processes for fabricating semiconductor devices often require that a suitable workpiece be subjected to a sequence of discrete process operations that involve optical radiation. Many of these processes are very sensitive to the process conditions and are preferably carried out within individual process chambers, often referred to as process tools, within which very specific conditions are established. Modern manufacturing facilities for such process tools typically use robotic transfer mechanisms as part of the overall automation of the production process.
The ability to establish and maintain precise conditions within the process chambers accurately and reproducibly is needed for the successful production of numerous types of products. Examples of products of particular importance are some of the state-of-the-art electronic devices such as semiconductor devices, flat panel display devices, and lithography masks. In order to achieve the high device yields and performance necessary for commercial success, the conditions within a process chamber are, in some cases, continuously monitored and controlled using sensors designed to measure specific physical parameters. Typically, these control sensors are built into the process tool so as to measure the parameter of interest such as optical radiation at a specific location within the process tool.
For applications such as the plasma processing of workpieces using a glow discharge, the techniques typically available for monitoring the plasma process conditions can suffer from a variety of problems. A typical problem is that the standard methods are intrusive in that they require modifications to the process chamber or process operating conditions. Another problem with the standard methods is that the standard methods typically provide only global measurements or averaged measurements for a region of the process. In general, currently available monitoring techniques and apparatuses cannot easily provide non-intrusive, spatially and/or temporally resolved measurements of optical radiation parameters for processing a substrate.
It is within this context that embodiments of the present invention arise.